Sperm vs. Gravity

A recent article by Lundsberg in the journalFertility and Sterility touched on one thing I have been wondering about. Based on a survey of 1000 American women, researchers found that 30-40% of women believe that “laying on one’s back with hips raised can increase the chance of getting pregnant” or “certain sexual positions can increase the chance of getting pregnant.”

A couple we interviewed for our book mentioned postcoital hip elevation. One woman described this as a "what-the-hell" intervention that she tried after reading about it on a message board or something.

However, Lundberg files that under misperceptions and misconceptions and cites a study by Kunz, which states that “rapid transport of the spermatozoa through the female genital tract is under the endocrine control of the dominant follicle, ensuring the preferential accumulation of spermatozoa at the site of fertilization.”

That makes it all perfectly clear, right?

Actually, I was so intimidated by that article that I only read the abstract.

So then I googled this question—and fell into a deep Internet rabbit hole.

Lots of articles say that this is an unfounded myth, and lots say that it's potentially helpful. For example, here’s a WebMD article quoting a few doctors claiming that elevating the pelvis after sex can increase the chances of conception. Here’s a completely unscientific yet fun article about sexual positions that influence conception. (This leads to another tangent about whether female orgasm is related to conception. Another Psychology Today contributor has reviewed this research here.)

Switching to PubMed, I found a beautifully written yet dense and, again, intimidating article about how sperm make their travels. It presents the female reproductive tract as a kind of obstacle course designed to weed out the weak sperm. It refers to research by Baker and Bellis about how much “flowback” sperm is lost after coitus. No mention is made of whether tilting the pelvis can make things any easier for the sperm, but the reminds us that, as we discussed previously sperm can hang out for up to five days waiting for an egg. Given that, it seems like assisting them with gravity for 15-20 postcoital minutes would not really make much difference, right? Then again, perhaps those are unusually strong sperm; perhaps others could benefit from some help?

More searching led to an article promoting “conception pillows”, and it based this assertion on a study by Saleh from 2000. In this study, women with unexplained infertility undergoing intrauterine insemination (IUI) were randomized to either rest in bed 10 minutes after the procedure or move about afterwards. Bed rest really helped: 29% of those who rested got pregnant, compared with 10% of those who did not. (Since the women were randomized to the two groups, it's unlikely that some other factor caused the difference.) However, the article said nothing about women elevating their hips. Plus, IUI is different than trying to conceive the old-fashioned way.

Then, because I care about giving my readers good information, I forced myself to read the Kunz article. Although I understood only about half of it, the main point is that uterine contractions draw the sperm toward their target and that these contractions are stronger right before ovulation. Mere gravity will not stop this process. However, it did not address the issue of whether working with gravity could help things along.

There were several points in this search when I wondered if there was any use to this inquiry.

However, it is a reminder that people – whether in person or on the Internet – will assert something as established fact when actually evidence is lacking to prove or disprove it. And this deluge of contradictory information can be maddening for women trying to conceive. And, really, anyone trying to make a health-related decision.

These strong assertions may give us a feeling of having more control or certainty than we have. We risk and numbing ourselves out with busyness and the search for new interventions.

Don't feel foolish trying something that is safe and harmless if your intuition tells you it might work. Perhaps there’s no evidence for it, just as there’s no evidence for welcoming the fetal spirit into your uterus. But maybe there’s no evidence against it – despite strongly worded opinions to the contrary.